bottle is Stamped DOT-3AA-2015 (pressure tested safe work rating)
Just want to be certain this idea sounds safe and effective to the experts for 10X burst disk hybrid.

Basically remove the valve from the tank and install a Schedule 80 Pipe Adapter to 2" shedule 40 theaded barrel. In this adapter I will drill and tap two locations with 1/8NPT thread.. one for the ignition module, and the other for charging and fueling. In reality I will only fire 7X via remote control and 4X shoulder fire.
HGDT predicts 4,200 ft lbs of muzzle energy at 4x and 500PSI pressures...
Remote fired at 7X it would achieve 6,500 ft lbs and 913 chamber pressures.

Will such a design prove effective? also is it safe for shoulder fire?
What happens if get a DDT? I cant imagine how I could build this to be any more safe.

Actually Ive looked at some ballistics charts .50 BMG was listed as 12,700 ft/lbs So Im only half that. Ive fired thousands of rounds out of an M2 .50 cal machine gun and although I cant say Ive shoulder fired one lmao... and it has a recoil system, and it can make a 9,000 lb armored HMMMWV rock back and fourth I would think something 1/3 the power could be safely shoulder fired. Im guessing the system would weigh about 50lbs so not too horrific.

I think shoulder firing at 4x should be ok, as long as you have a good grip on the gun there's no reason it can't be handled.

The problem with the oxygen tank is its small opening, how do you plan on mitigating that? Not sure if you covered that when talking about the sch80 adapter but you'll want to drill a bigger porting in to the tank and weld some threads in. I would say a 1.5" - 2 " porting would be good. If you don't enlarge the porting, you're just wasting an oxy tank.

Ive seen your vids on you tube... big fan. Anyway a 1.5" barel would be ok too, plus would reduce the packaging weight. and by a 20 cubic foot I want to make sure everyone unfamiliar with welding knows its only a 5" x 14" bottle weighing 15 lbs with 274 cubic inches... 20 cubic foot is compressed oxy volume.

Assuming your fittings are all up to it, should be a much safer project than your last effort

As to barrel size, MrC makes a good point - remember that a 2" hole allows 4 times the flow as a 1" hole. Still, in spite of this it would still be bloody impressive with a 2 inch barrel. Also, it would seem a pity to waste such a large chamber on a small bore, but on the other hand you would get great performance without having to use higher mixes.